Electrodeposition method utilizing quaternary phosphonium group-containing resins

ABSTRACT

Synthetic resins containing quaternary phosphonium base groups are prepared by reacting an epoxy group-containing material with a phosphine in the presence of an acid. The resins may contain epoxy groups or they may be essentially epoxy-group free, and may optionally contain oxyalkylene groups. When dispersed in water, the aqueous dispersion preferably contains boron. The resultant dispersion can be applied to a wide variety of substrates by electrodeposition and will deposit on the cathode to provide coatings of unique properties, including high resistance to corrosion and staining.

United States Patent Bosso et a1.

[451 July 15,1975

15 1 ELECTRODEPOSITION METHOD UTILIZING QUATERNARY PHOSPHONIUMGROUP-CONTAINING RESINS [75] Inventors: Joseph F. 30550, Lower Burrell;

Marco Wismer, Gibsonia. both of Pa.

[73] Assignee: PPG Industries, Inc., Pittsburgh, Pa.

[22] Filed: Apr. 3, 1974 [21] Appl. No.: 457,335

Related US. Application Data [63] Continuation-impart of Serv No.217,278, Jan. 12,

1972, abandoned.

[52] US. Cl. 204/181 [51] Int. Cl BOlk 5/02 [58] Field of Search 204/181[56] References Cited UNITED STATES PATENTS 3,619,398 11/1971 Bossoet a1204/181 1(0ra1 et al. 204/181 Beck et a1 204/181 [57] ABSTRACT Syntheticresins containing quaternary phosphonium base groups are prepared byreacting an epoxy groupcontaining material with a phosphine in thepresence of an acid. The resins may contain epoxy groups or they may beessentially epoxy-group free, and may optionally contain oxyalkylenegroups. When dispersed in water, the aqueous dispersion preferablycontains boron. The resultant dispersion can be applied to a widevariety of substrates by electrodeposition and will deposit on thecathode to provide coatings of unique properties, including highresistance to corrosion and staining.

11 Claims, No Drawings ELECTRODEPOSITION METHOD UTILIZING QUATERNARYPHOSPI-IONIUM GROUP-CONTAINING RESINS CROSS-REFERENCE TO RELATEDAPPLICATIONS This application is a continuation-in-part of copendingapplication Ser. No. 217,278, filed Jan. 12, 1972, now abandoned.

BACKGROUND OF THE INVENTION Electrodeposition, although known for sometime, has only recently become of commercial importance as a coatingapplication method. While many compositions can be electrodeposited,most coating compositions when applied using electrodepositiontechniques do not produce commercially usable coatings. Moreover,electrodeposition of many coating materials, even when otherwisesuccessful, is attended by various disadvantages, such as non-uniformcoatings and poor throw power. In addition, the coatings obtained are,in most instances, deficient in certain properties essential for theirutilization in many applications for which electrodeposition isotherwise suited. ln particular, properties such as corrosion resistanceand alkali resistance are difficult to achieve with resinsconventionally employed in electrodeposition processes. Likewise,staining and yellowing on baking or aging are problems which must be metto produce a commerciallysuccessful resin for many applications. Anionicresins, due to their acidic nature, tend to be sensitive to common typesof corrosive attack, for example, salts and alkalis. Manyelectrodepositable anionic coatings are subject to discoloration orstaining because of dissolution of metal ions at the anode, which isbeing coated.

Epoxy resins are among the most useful resins for many purposes and haveexcellent corrosion resistance and other properties. They are employedin many coatings, but have not been employed in water-dispersiblecompositions suitable for application by electrodeposition because theycannot be adequately dispersed in water under the conditions required insuch processes. Esterified epoxies have been utilized, but these actsimilarly to the polycarboxylic acid resins, and while offering manyadvantages over such polycarboxylic acid resins, are still subject tomany of their disadvantages.

Recently, there has been developed a group of waterdispersible,quaternary ammonium salt-containing resins which have utility as coatingresins in general, and particularly, in aqueous electrodepositablecompositions.

These resins are prepared by reacting an epoxygroup containing organicmaterial, preferably a resin which is a polyepoxide containing aplurality of epoxy groups with an amine acid salt, yielding a resinpreferably containing epoxy groups and containing quaternary ammoniumsalt groups.

DESCRIPTION OF THE INVENTION It has now been found that syntheticresins, which are prepared by reacting an epoxy group-containing organicmaterial with a phosphine in the presence of an acid, and which areungelled water-dispersible resins containing chemicallybound quaternaryphosphonium base groups and optionally containing epoxy groups and/oroxyalkylene groups can be utilized to provide clear or colloidal watersolutions or dispersions. These compositions, when solubilized throughionization of the quaternary group and acid counterion, preferably wherethe acid counter-ion is derived from an acid having a dissociationconstant greater than 1 X 10*, can be applied by electrodeposition toprovide adherent coatings having excellent properties. Whenelectrodeposited, they deposit on the cathode. When employed in aqueouscompositions for electrodeposition, the above resins form the majorresinous constituent of the composition, either as the sole resinouscomponent or along with one or more other resinous or film-formingmaterials or crosslinking agents. When dispersed in water, the aqueouscomposition preferably contains boron.

Among the properties of the coatings herein are the desirable propertiesordinarily associated with electrodepositable resins known heretoforeand, in addition, the compositions herein provide coatings of uniqueadvantages and properties. These include a high level of resistance tosalt spray, alkali and similar corrosive elements, even over unprimedmetals or untreated metals and in the absence of corrosion inhibitingpigments.

The coatings are resistant to staining and discoloration which is oftenencountered with electrodeposited coatings based upon anionic typeresins. Further, the resins of the invention have a substantial degreeof resistance to yellowing on baking or aging and, therefore, aresuitable for forming white or pastel colored coatings.

The resins of the invention are ungelled, waterdispersible resins havingin their molecule chemicallybound quaternary phosphonium base salts, thequaternary phosphonium base salts preferably being salts of an acidhaving a dissociation constant greater than l X 10 including organic andinorganic acids. Upon solubilization, at least a portion of the salt ispreferably a salt of an acid having a dissociation constant greater than1 X 10 Optionally the resins can contain epoxy groups and/or oxyalkylenegroups.

The quaternary phosphonium base salts are preferably salts of an organiccarboxylic acid since it has been found that the use of such acidsenhances the dispersibility of the compositions disclosed herein. Thepresently preferred acid is lactic acid. Preferably the resin containsat least about 0.1 percent and up to about 35 percent by weightphosphorus in the form of chemically-bound quaternary phosphonium basesalt groups.

The resins of the invention are formed by reacting an epoxygroup-containing organic material with a phosphine in the presence of anacid to form quaternary phosphonium base salt group-containing resins.

The epoxy group-containing organic material can be any monomeric orpolymeric compound or mixture of compounds having a l,2-epoxy group. Itis preferred that the epoxy-containing material have a l,2-epoxyequivalency greater than 1.0, that is, in which the average number of1,2-epoxy groups per molecule is greater than 1. It is preferred thatthe epoxy compound be resinous, that is, a polyepoxide, i.e., containingmore than one epoxy group per molecule. The polyepoxide can be any ofthe wellknown epoxides. Examples of these polyepoxides have, forexample, been described in U.S. Pat. Nos. 2,467,171; 2,615,007;2,716,123; 3,030,336; 3,053,855 and 3,075,999.

A preferred class of polyepoxides are the polyglycidyl ethers ofpolyphenols, such as Bisphenol A. These may be produced, for example, byetherification of a polyphenol with epichlorohydrin or dichlorohydrin inthe presence of an alkali. The phenolic compound may be bis(4-hydroxyphenyl) l l -ethane, bis(4-hydroxyphenyl) l l -isobutane;bis(4-hydroxytertiarybutylphenyl)2,2-propane,bis(2-hydroxynaphthyl)methane, l,S-dihydroxynaphthalene, or the like.Another quite useful class of polyepoxides are produced similarly fromnovolak resins or similar polyphenol resins.

Also suitable are the similar polyglycidyl ethers of polyhydric alcoholswhich may be derived from such polyhydric alcohols as ethylene glycol,diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, glycerol,bis(4-hydroxycyclohexyl)2,2-propane, and the like.

There can also be used polyglycidyl esters of polycarboxylic acids whichare produced by the reaction of epichlorohydrin or a similar epoxycompound with an aliphatic or aromatic polycarboxylic acid, such as oxalic acid, succinic acid, glutaric acid, terephthalic acid,2,6-naphthylene dicarboxylic acid, dimerized linolenic acid, and thelike. Examples are diglycidyl adipate and diglycidyl phthalate.

Also useful are polyepoxides derived from the epoxidation of anolefinically unsaturated alicyclic compound. Included are diepoxidescomprising in part one or more monoepoxides, These polyepoxides arenonphenolic and are obtained by epoxidation of alicyclic olefins, forexample, by oxygen and selected metal catalysts, by perbenzoic acid, byacetaldehyde monoperacetate, or by peracetic acid. Among suchpolyepoxides are the epoxyalicyclic ethers and esters, which are wellknown in the art.

Another often-preferred class of polyepoxides are those containingoxyalkylene groups in the epoxy molecule. Such oxyalkylene groups aretypically groups of the general formula:

where R is hydrogen or alkyl, preferably lower alkyl (e.g., having 1 to6 carbon atoms) and where, in most instances, m is 1 to 4 and n is 2 to50. Such groups can be pendent to the main molecular chain of thepolyepoxide or part of the main chain itself. The proportion ofoxyalkylene groups in the polyepoxide depends upon many factors,including the chain length of the oxyalkylene groups, the nature of theepoxy and the degree of water solubility desired. Usually the epoxycontains at least about 1 percent by weight or more, and preferablypercent or more, of oxyalkylene groups.

Some polyepoxides containing oxyalkylene groups are produced by reactingsome of the epoxy groups of a polyepoxide, such as the epoxy resinsmentioned above, with a monohydric alcohol containing oxyalkylenegroups. Such monohydric alcohols are conveniently produced byoxyalkylating an alcohol, such as methanol, ethanol, or other alkanol,with an alkylene oxide. Ethylene oxide, 1,2-propylene oxide and 1,2-butylene oxide are especially useful alkylene oxides. Other monohydricalcohols can be, for example, the commercially-available materials knownas Cellosolves and Carbitols, which are monoalkyl ethers of polyalkyleneglycols. The reaction of the monohydric alcohol and the polyepoxide isgenerally carried out in the presence of a catalyst. Formic acid,dimethylethanolamine, diethylethanolamine, N.N-dimethylbenzylamine, and,in some cases, stannous chloride, are useful for this purpose.

The polyepoxide employed to produce the foregoing epoxies containingoxyalkylene groups should contain a sufficient number of epoxy groups sothat the average number of residual epoxy groups per molecule remainingin the product after the oxyalkylation is greater than 1.0. Whenoxyalkylene groups are present, the epoxy resin preferably contains fromabout 1 to about percent or more by weight of oxyalkylene groups.

Other epoxy-containing compounds and resins include nitrogeneousdiepoxides such as disclosed in U.S. Pat. No. 3,365.47]; epoxy resinsfrom l,l-methylene bis(5-substituted hydantoin), U.S. Pat. No.3,391,097; bisimide containing diepoxides, US. Pat. No. 3,450,71 l;epoxylated aminomethyldiphenyl oxides, U.S. Pat. No. 3,312,664;heterocyclic N,N'-diglycidyl compounds, U.S. Pat. No. 3,503,979; aminoepoxy phosphonates, British Pat. No, l,l72,9l6; 1,3,5- triglycidylisocyanates, as well as other epoxycontaining materials known in theart.

Another preferred class of resins which may be employed are acrylicpolymers containing epoxy groups. These acrylic polymers are preferablypolymers formed by copolymerizing an unsaturated epoxy-containingmonomer, such as glycidyl acrylate or methacrylate.

Any polymerizable monomeric compound containing at least one Ch =Cgroup, preferably in terminal position, may be polymerized with theunsaturated glycidyl compounds. Examples of such monomers include:

l. Monoolefinic and diolefinic hydrocarbons, that is, monomerscontaining only atoms of hydrogen and carbon, such as styrene,alpha-methyl styrene, alpha-ethyl styrene, isobutylene (2-methylpropene-l 2- methylbutene-l, Z-methyl-pentene-l, 2,3-dimethylbutene-l,2,3-dimethyl pentene-l, 2,4-dimethyl pentene-l, 2,3,3-trimethylbutene-l, 2-methyl heptene-l, 2,3-dimethyl hexene-l, 2,4-dimethylhexene-l, 2,5- dimethyl hexene-l, 2-methyl-3-ethyl pentene-l, 2,3,3-trimethyl pentene-l, 2,3,4-trimethyl pentene-l, 2- methyl octene-l2,6-dimethyl heptene-l, 2,6-dimethyl octene-l, 2,3-dimethyl decene-l,Z-methyl nonadecene-l, ethylene, propylene, butylene, amylene, hexylene,butadiene-l ,3, isopropene, and the like;

2. Halogenated monoolefinic and diolefinic hydrocarbons, that is,monomers containing carbon, hydrogen, and one or more halogen atoms,such as alphachlorostyrene, alpha-bromostyrene, 2,5- dichlorostyrene,2,5-dibromostyrene, 3,4- dichlorostyrene, ortho-, metaandpara-fluorostyrenes, 2,6-dichlorostyrene, 2,6-difluorostyrene,3-fluoro-4- chlorostyrene, 3-chloro-4-fluorostyrene, 2,4,5-trichlorostyrene, dichloromonofluorostyrenes, 2- chloropeopene,2-chlorobutene, 2-chloropentene, 2-

chlorohexene, 2-chloroheptene, 2-bromobutene, 2- bromoheptene,2-fluorohexene, 2-fluorobutene, 2- iodopropene, 2iodopentene,4-bromoheptene, 4-

chloroheptene, 4-fluoroheptene, cisand trans-1,2- dichloroethylenes,l,2-dibromoethylene, 1,2- difluoroethylene, 1,2-diiodoethylene,chloroethylene (vinyl chloride), l,l-dichloroethylene (vinylidenechloride), bromoethylene, fluoroethylene, iodoethylene,l,l-dibromoethylene, l,l-fluoroethylene, 1,1- diiodoethylene, 1,l,2,2-tetrafluoroethylene, l-chloro- 2,2.2-trifluoroethylene,chlorobutadiene and other halogenated diolefinic compounds;

3. Esters of organic and inorganic acids, such as vinyl acetate. vinylpropionatc, vinyl butyrate, vinyl isobutyr ate, vinyl valarate, vinylcaproate. vinyl enanthate. vinyl benzoate, vinyl toluate,vinyl-p-chlorobenzoatc. vinyl-o-chlorobenzoatc and similar vinylhalobcnzoates, vinyl-p-methoxybenzoate, vinyl-omethoxybenzoate,vinyl-p-ethoxybenzoate. methyl methacrylate, ethyl methacrylate, propylmethacrylate. butyl methacrylatc, amyl methacrylate, hexyl methacrylate,heptyl methacrylate, octyl methacrylate, decyl methacrylate, methylcrotonate, and ethyl tiglate;

Methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate,butyl acrylate, isobutyl acrylate, amyl acrylate, hexyl acrylate,Z-ethylhexyl acrylate, heptyl acrylate, octyl acrylate,3,5,5-trimethylhexyl acrylate, decyl acrylate, and dodecyl acrylate;

lsopropenyl acetate, isopropenyl propionate, isopropenyl butyrate,iospropenyl isobutyrate, isopropenyl valerate, isopropenyl caproate,isopropenyl enanthate, isopropenyl benzoate,isopropenyl-p-chlorobenzoate, isopropenyl-o-chlorobenzoate,isopropenyl-obromobenzoate, isopropenyl-m-chlorobenzoate, isopropenyltoluate, isopropenyl alpha-chloroacetate, and isopropenylalpha-bromopropionate;

Vinyl alpha-chloroacetate, vinyl alphabromoacetate, vinylalpha-chloropropionate, vinyl alpha-bromopropionate, vinylalpha-iodopropionate, vinyl alpha-chlorobutyrate, vinylalpha-chlorovalerate and vinyl alphabromovalerate;

Allyl chloride, allyl cyanide, allyl bromide, allyl fluoride, allyliodide, allyl chlorocarbonate, allyl nitrate, allyl thiocyanate, allylformate, allyl acetate, allyl propionate, allyl butyrate, allylvalerate, allyl caproate, allyl-3,5,5-trimethyl hexoate, allyl benzoate,allyl acrylate, allyl crotonate, allyl oleate, allyl chloroacetate,allyl trichloroacetate, allyl chloropropionate, allyl chlorovalerate,allyl lactate, allyl pyruvate, allyl monoacetate, allyl acetoacetate,allyl thioacetate, as well as methallyl esters corresponding to theabove allyl esters, as well as esters from such alkenyl alcohols asbetaethyl allyl alcohol, beta-propyl allyl alcohol, l-butene- 4-ol,2-methyl-butene-4-Ol, 2(2,2-dimethylpropyl)-lbutene-4-ol, andl-pentene-4-ol;

Methyl alpha-chloroacrylate, methyl alphabromoacrylate, methylalpha-fluoroacrylate, methyl alpha-iodoacrylate, ethylalpha-chloroacrylate, propyl alpha-chloroacrylate, isopropylalpha-bromoacrylate, amyl alpha-chloroacrylate, octylalpha-chloroacrylate, 3,5,5-trimethylhexy] alpha-chloroacrylate, decylalphachloroacrylate, methyl alpha-cyanoacrylate, ethylalpha-cyanoacrylate, amyl alpha-cyanoacrylate and decyl alpha-cyanoacrylate;

Dimethyl maleate, diethyl maleate, diallyl maleate, dimethyl fumarate,diethyl fumarate, dimethallyl fumarate and diethyl glutaconate;

4. Organic nitriles, such as acrylonitrile, methacrylonitrile,ethacrylonitrile, 3-octenenitrile, crotonitrile, oleonitrile, and thelike.

In carrying out the polymerization reaction, techniques well known inthe art may be employed. A peroxygen type catalyst is ordinarilyutilized. Diazo compounds or redox catalyst systems can also be employedas catalysts.

The acrylic polymer may likewise be prepared with monomers of the typesuch that the final polymer contains potential crosslinking sites. Suchmonomers include acrylamides or methacrylamides, their N- methylol orN-methylol ether derivatives; unsaturated monomers containing cappedisocyanate groups, or aziridyl groups; and hydroxy-containingunsaturated monomers, for example, hydroxyalkyl acrylates.

Another method of producing acrylic polymers which may be utilized inthis invention is to react an acrylic polymer containing reactive sites,such as carboxyl groups or hydroxyl groups, secondary amine groups orother active hydrogen-containing sites, with an epoxy-containingcompound such as the diglycidyl ether of Bisphcnol A or otherpolyepoxides as enumerated elsewhere herein, to provide anepoxy-containing acrylic polymer. I

Vinyl addition polymers which contain alicyclic unsaturation can beepoxidized to form an epoxy groupcontaining polymer.

Yet another class of polymers which are useful in preparing the resinsof this invention are isocyanate group-containing polyurethanes. Theisocyanateterminated polyurethane prepolymers employed as startingmaterials according to the present invention may be obtained by thereaction of a selected polymeric glycol. The polyurethane polymersinclude those which are prepared from polyalkylene ether glycols anddiisocyanates. The term polyalkylene ether glycol as used herein refersto a polyalkylene ether which contains terminal hydroxy groups. Thesecompounds are derived from the polymerization of cyclic ethers such asalkylene oxides or dioxolane or from the condensation of glycols. Theyare sometimes known as polyoxyalkylene glycols, polyalkylene glycols, orpolyalkylene oxide glycols, or dihydric polyoxyalkylenes. Those usefulin preparing the products of this invention may be represented by theformula HO(RO),,H, in which R stands for an alkylene radical and n is aninteger. Glycols containing a mixture of radicals, as in the compoundHO(Cl-l- OC H O),,H, or HO(C H O),,(C H O),,,(C H O),,H, can be used.These glycols are either viscous liquids or waxy solids.Polytetramethylene ether glycols, also known as polybutylene etherglycols, may be employed. Polyethylene ether and polypropylene etherglycols, having the above-indicated formula, are among the preferredglycols. Polyethylene ether glycols, poly-1,2-pr0pylene ether glycols,and poly-1,2- dimethyl ethyl ether glycols are representative of otheroperative compounds. The presently preferred glycols are polypropyleneglycols with a molecular weight between about 300 and about 1,000.

Any of a wide variety of organic polyisocyanates may be employed inreaction, including aromatic, aliphatic, and cycloaliphaticdiisocyanates and combinations of these types. Representative compoundsinclude aromatic diisocyanates, such as 2,4-tolylene diisocyanate,mixtures thereof with 2,6-t0lylene diisocyanates (usually about /20),4,4-methylenebis(phenylisocyanate) and m-phenylene diisocyanate.Aliphatic compounds such as ethylene diisocyanate, methylenediisocyanate, propylene-l,2-diisocyanate, butylene-l,3-diisocyanate,tetramethylene diisocyanate, hexamethylene diisocyanate, anddecamethylene diisocyanate and alicyclic compounds, such as 1.2- andl,4-cyclohexylene diisocyanates, 4,4-methylene-bis(-cyclohexylisocyanate) and isophorone diisocyanate are also operable.Arylene diisocyanates, i.e., those in which each of the two isocyanategroups is attached directly to an aromatic ring, react more rapidly withthe polymeric glycols than do the alkylene diisocyanates. Compounds suchas 2,4-tolylene diisocyanate in which the two isocyanate groups differin reactivity are particularly desirable. The diisocyanates may containother substituents, although those which are free from reactive groupsother than the two isocyanate groups may be attached either to the sameor to different rings. Additional polyisocyanates which may be employed,for example, include: p,p'-diphenylmethane diisocyanate,3,3"dimethyl-4,4-biphenylene diisocyanate. 3,3-dimethoxyoxy-4,4'-biphenylene diisocyanate, 3.3-diphenyl-4,4'-biphenylene diisocyanate, 4-chloro-l,3- phenylenediisocyanate, 3,3-dichloro-4,4'- biphenylene diisocyanate, and1,5-naphthalene diisocyanate, and other polyisocyanates in a blocked orsemiinactive form such as bis-phenylcarbamates or tolylene diisocyanate,p,p'-diphenylmethane diisocyanate, p-phenylene diisocyante, and1,5-naphthalene and l,S-tetrahydronaphthalene diisocyanate.

Instead of the hydrocarbon portion of the polyether glycols used informing these polyurethane products being entirely alkylene, it cancontain arylene or cycloalkylene radicals together with the alkyleneradicals as, for example, in the condensation product of a polyalkyleneether glycol with alpha, alpha'-dibromo-pxylene in the presence ofalkali. In such products, the cyclic groups inserted in the polyetherchain are preferably phenylene, naphthalene or cyclohexylene radicals orthose radicals containing alkyl or alkylene substituents, as in thetolylene, phenylethylene or xylene radicals.

Also included in the polyurethane products are those made from asubstantially linear polyester and an organic diisocyanate of the typepreviously described. Products of this sort are described in U.S. Pat.Nos. 2,621,166; 2,625,531 and 2,625,532. The polyesters are prepared byreacting together glycols such as ethylene glycol, diethylene glycol,triethylene glycol, trimethylene glycol, 1,2-propylene glycol,tetramethylene glycol, 2,3-butylene glycol, pentamethylene glycol, anddicarboxylic acids such as malonic, maleic, succinic, adipic, pimelic,sebacic, oxalic, phthalic, terephthalic, hexahydroterephthalic, andpara-phenylene diacetic acids, decamethylene dicarboxylic acid, and thelike. Another useful group of compounds for this purpose are thepolyester amide resins having terminal hydroxyl groups. The preferredpolyesters may be represented by the formula HO-EBOOCB'-COO],,BOH inwhich B and B are hydrocarbon radicals derived from the glycol anddicarboxylic acid respectively and n is an integer. 1n the preparationof these polyesters, the glycol is used in at least slight excess sothat the polyesters contain terminal hydroxyl groups which are availablefor reaction with the isocyanates. The same polyisocyanates and reactionconditions useful in preparing polyurethanes from the polyalkylene etherglycols are also useful with the polyesters.

Polyurethane glycols may also be reacted with an organic polyisocyanateto give isocyanate-terminated polyurethanes for use as startingmaterials in the present invention. The starting polyurethane glycol isprepared by reacting a molar excess of a polymeric glycol with anorganic diisocyanate. The resulting polymer is a polyurethane containingterminal hydroxyl groups which may then be further reacted withadditional polyisocyanate to produce the starting isocyanateterminatedpolyurethane prepolymer.

Another starting polyurethane prepolymer may be such as disclosed in US.Pat. No. 2,861,981, namely, those prepared from a polyisocyanate and thereaction product of an ester of an organic carboxylic acid with anexcess of a saturated aliphatic glycol having only carbon atoms in itschain and a total of 8 to l4 carbon atoms, at least one two-carbon atombranch per molecule, and having terminal hydroxy groups separated by atleast six carbon atoms.

It is obvious, from the above-described methods by which thepolyurethane reaction products may be prepared and from the reactantsused, that these products will contain a plurality of intralinearradicals of the formula NHCOOXO--CONH, wherein the bivalent radical OXOis obtained by removing the terminal hydrogen atoms of the polymericglycol, said glycol being selected from the group consisting ofpolyalkylene ether glycols, polyurethane glycols, polyalkylene aryleneether glycols, polyalkylenecycloalkylene ether glycols, polyalkyleneetherpolythioether glycols, polyester amide glycols of the formula:

where B and B are hydrocarbon radicals and n is an integer, and that atypical isocyanate-terminated polyurethane polymer produced fromdiisocyanates and dihydric glycols will, on an average, contain at a 2:1NCOOH ratio, a plurality of intralinear molecules conforming to theformula:

wherein OXO- has the value given previously and Y is the polyisocyanatehydrocarbon radical.

1n the preparation of the starting polyurethane polymer, an excess ofthe organic polyisocyanate of the polymeric glycol is used, which may beonly a slight excess over the stoichiometric amount (i.e., oneequivalent of polyisocyanate for each equivalent of the polymericglycol). In the case of a diisocyanate and a dihydric polyalkyleneether, the ratio of NCO to OH of the polyol will be at least one and maybe up to a 3:1 equivalent ratio. The glycol and the isocyanate areordinarily reacted by heating with agitation at a temperature of 50 to130C., preferably to C. The ratio of organic polyisocyanate compound topolymeric glycol is usually and preferably between about 1.3:1 and 20:1.

The reaction is preferably, but not necessarily, effected in the absenceof a solvent, when the prepolymer is a fluid at processing temperatures.When it is not, or when it is desired to employ a solvent, convenientsolvents are inert organic solvents having a boiling range of about 90C.when the reaction is to be carried out in open equipment. Lower boilingsolvents may, of course, be used where the reaction is carried out inclosed equipment to prevent boiling off the solvent at the temperaturesof the reaction. Solvents boiling at substantially more than C. aredifficult to remove from a final chain-extended elastomer at desirableworking temperatures, althought it will be obvious that higher boilingsolvents may be employed where the excess solvent is removed by meansother than by heating or distillation. The solvent, when used, may beadded at the beginning, at an intermediate point, or at the end of theprepolymer reaction stage, or after cooling of the formed prepolymer.The solvents to be used are preferably those in which the reactants havesome solubility but in which the final chain-extended product isinsoluble. Ketones, tertiary alcohols and esters may be used. Thealiphatic hydrocarbon solvents such as the heptanes, octanes andnonanes, or mixtures of such hydrocarbons obtained fromnaturally-occurring petroleum sources such as kerosene, or fromsynthetically prepared hydrocarbons, may sometimes be employed.Cycloaliphatic hydrocarbons such as methylcyclohexane and aromatichydrocarbons such as toluene may likewise be used. Toluene and isopropylacetate are preferred solvents. The amount of solvent used may be variedwidely. From 25 to 400 parts of solvent per 100 parts of glycol havebeen found to be operable. The excess solvent, where large amounts areemployed, may be separated partially or completely from the polymerprior to emulsification in the water solution. If an emulsion techniqueis to be employed in the chain extension; sometimes the excess solventis useful and is allowed to remain during the emulsification stage.

The reactants are cooked for a period sufficient to react most, if notall, of the hydroxy groups, whereafter the prepolymer is allowed tostand and the free NCO content determined.

Usual pHs are employed during preparation of the prepolymer, thereaction preferably being maintained substantially neutral. Basesaccelerate the reaction, acids retard the reaction, and preferablyneither are added.

These isocyanate group-containing polyurethanes are then reacted with anepoxy-containing compound such as glycidol, for example, at temperaturesof about 25 to about 45C., usually in the presence of a catalyst whichpromotes urethane formation.

The resins of the invention are formed by reacting the epoxy compoundwith a phosphine in the presence of an acid to form quaternaryphosphonium base group-containing resins.

The phosphine employed may be virtually any phosphine which does notcontain interferring groups. For example, the phosphine may bealiphatic, aromatic or cyclic. Examples of such phosphines includetrimethyl phosphine, triethyl phosphine, tripropyl phosphine, tributylphosphine, phenyl dimethyl phosphine, phenyl diethyl phosphine, phenyldipropyl phosphine, diphenyl methyl phosphine, diphenyl ethyl phosphine,dipehnyl propyl phosphine, triphenyl phosphine, tetramethylene methylphosphine and the like.

The acid employed may be virtually any acid which forms a quaternaryphosphonium salt. Preferably the acid is an organic carboxylic acid.Examples of acids which may be employed are boric acid, lactic acid,formic acid, acetic acid, propionic acid, butyric acid, hydrochloricacid, phosphoric acid, and sulfuric acid. Preferably the acid is an acidhaving a dissociation constant greater than about 1 X the presentlypreferred acid being lactic acid.

The ratio of phosphine to acid is not unduly critical. Since one mole ofacid is utilized to form one mole of phosphonium group, it is preferredthat at least about 1 mole of acid be present for each mole of desiredphosphine-to-phosphoniurn conversion.

The phosphine-acid mixture and the epoxy compound are reacted by mixingthe components, usually at moderately elevated temperatures such as 70to l 10C., since it has been found that quaternary phosphonium groupsare not generally formed at lower temperatures. A solvent is notnecessary, although one is often used in order to afford better controlof the reaction. Aromatic hydrocarbons, monoalkyl ethers of ethyleneglycol, aliphatic alcohols are suitable solvents.

The proportions of the phosphine and the epoxy compound can be variedand the optimum proportions depend upon the particular reactants.Ordinarily, however, from about one part to about 50 parts by weight ofthe phosphine per parts of epoxy compound is employed. The proportionsare usually chosen with reference to the amount of phosphorus, which istypically from about 0.1 to about 35 percent, based on the total weightof the phosphine-acid mixture, and the epoxy compound. Since thephosphine salt reacts with the epoxide groups of the epoxy resinemployed, in order to provide an epoxy group-containing resin, lessphosphine than the stoichiometric equivalent of the epoxide groupspresent is employed, so that the final resin is provided with one epoxygroup per average molecule. Similarly, if an essentially epoxy-freeresin is desired, a stoichiometric amount or excess of phosphine isused.

It is also to be recognized that useful compositions can be produced byfirst reacting a phosphine with an epoxy containing organic material,and then adding an acid and subsequently heating the reaction mixture toa suitable reaction temperature. The phosphine and the epoxy groups arereacted until a tertiary phosphine is formed. The addition of the acidthen forms a tertiary phosphine-acid mixture, which mixture, uponheating, will then react with any residual epoxy groups present. In theevent no epoxy groups are present after the phosphine-acid mixtureformation is complete, additional epoxy material must be added.

Regardless of the method chosen to produce the composition of theinstant invention, the critical reaction which forms quaternaryphosphine salt is that between a tertiary phosphine-acid mixture and theepoxy group or groups of the epoxy containing material.

The aqueous dispersions of the instant invention may also contain boron.The boron can be added to the dispersion by adding an aqueous solutionof boric acid, boric acid itself, or a compound hydrolyzable to formboric acid in aqueous medium. Alternatively, the acid utilized with thephosphine may be boric acid.

In still another embodiment, the epoxy compounds described above may bereacted with an ester of boric acid or a compound which can be cleavedto form boric acid in a medium containing water and preferably anamino-containing boron ester and/or a tertiary amine salt of boric acidto produce epoxy reaction products. If this approach is chosen, thefinal composition will contain quaternary ammonium groups. Thus, inorder to ensure that epoxy groups remain for the subsequent quaternaryphosphonium group formation, the amount of boron compound used should besuch that less than one equivalent of amine nitrogen (of the boroncompound) is present for every epoxy group present.

The hydrolyzable boron compound utilized in producing the reactionproducts or to be added to the dispersion can be, for example, anytriorganoborate in which at least one of the organic groups issubstituted with an amino group. Structurally, such esters are esters ofboric acid or a dehydrated boric acid such as metaboric acid andtetraboric acid, although not necessarily produced from such acids. Inmost cases the boron esters employed correspond to one of the generalformulas:

RO B/OR oR where R and R are hydrogen or preferably methyl, ethyl orother lower alkyl groups but can be essentially any other organicradical, so long as they do not interfere with the desired reaction. Thenature of the particular groups is less important than the presence ofan amino nitrogen atom, and thus higher alkyl, aryl, alkaryl, aralkyland substituted groups of these types can be present. While both R andR; can be hydrogen (i,e., the amino group is a primary amino group), itis preferred that at least one be an alkyl or other organic group, sothat the amino group is secondary or tertiary.

The preferred boron esters correspond to the formula'.

R and R being divalent organic radicals, such as alkylene or substitutedalkylene, e.g., oxyalkylene or poly- (oxyalkylene), or, less desirably,arylenc, alkarylene or substituted arylene. R and R, can be alkyl,substituted alkyl, aryl, alkaryl, or other residue from essentially anymonohydroxy alcohol derived by removal of the hydroxyl group. R and Rcan be the same or different.

Examples of boron esters within the above class include:2-(beta-dimethylaminoisopropoxy)-4,5-dimethyl- 1,3,2-dioxaborolane2-(beta-diethylaminoethoxy)-4,4,6-trimethyl-1,3,2-

dioxaborinane 2-(beta-dimethylaminoethoxy)-4,4,6-trimethyl-l ,3,2-

dioxaborinane 2-( beta-diisopropylaminoethoxy )-l ,3 ,2-dioxaborinane2-( beta-dibutylaminoethoxy )-4-methyll ,3 ,2-

dioxaborinane 2-( beta-diethylaminoethoxy l ,3 ,Z-dioxaborinaneZ-(gamma-aminopropoxy )-4-methyll ,3 ,2-

dioxaborinane 12 2-(beta-methylaminoethoxy)-4,4,6-trimethyl-1,3,2-

dioxaborinane 2-(beta-ethylaminoethoxy)-1,3,6-trioxa-2- boracyclooctane2-(gamma-dimethylaminopropoxy)- l ,3.6,9-tetraoxa-2- boracycloundecane2-(beta-dimethylaminoethoxy)-4-(4-hydroxybutyl)- 1,3,2-dioxaborolaneReaction product of (CH;,)- NCH CH OH lactic acid B 0 neopentyl glycol Anumber of such boron esters are known. Many are described, for example,in US. Pat. Nos. 3.301.804 and 3,257,442. They can be prepared byreacting one mole of boric acid (or equivalent boric oxide) with atleast 3 moles of alcohol, at least one mole of the alcohol being anamino-substituted alcohol. The reaction is ordinarily carried out byrefluxing the reactants with removal of the water formed.

The reaction of the boron compound may be conducted simultaneously withphosphonium group formation since the reaction conditions for thisreaction are similar.

The phosphine-acid mixture and the epoxy compound are preferably reactedby mixing the components in the presence of a sufficient amount of waterto provide an exothermally controlled reaction. The amount of wateremployed should be that amount of water which allows for smoothreaction. Typically, water is employed as the basis of about 1.75percent to about 20 percent by weight, based on total reaction mixturesolids, and preferably about 2 percent to about l5 percent by weight,based on total reaction solids.

The particular reactants, proportions and reaction conditions should bechosen in accordance with considerations well-known in the art, so as toavoid gellation of the product during the reactionv For example,excessively severe reaction conditions should not be employed.Similarly, compounds having reactive substituents should not be utilizedalong with epoxy compounds with which those substituents might reactadversely at the desired conditions.

The product forming the resin of the invention may be crosslinked tosome extent; however, it remains soluble in certain organic solvents andcan be further cured to a hard, thermoset state. It is significantlycharacterized by its chemically-bound quaternary phosphonium content.

Aqueous compositions containing the above reaction products are highlyuseful as coating compositions and can be applied by any conventionalmethod, such as by dipping, brushing, etc. They are, however, eminentlysuited to application by electrodeposition.

As previously indicated, the resins herein described may contain freeepoxy groups or may be essentially epoxy group free. The stoichiometryof the reactants forming quaternary phosphonium groups from the startingepoxy material is adjusted so that all epoxy groups are reacted or sothat epoxy groups remain for subsequent crosslinking. Alternatively,where free epoxy groups remain after quaternary phosphonium formation,they may be further reacted without crosslinking to modify the resinproperties.

Where the final resin has crosslinkable sites such as free epoxy groups,hydroxyl groups, or other reactive sites, there may be usefullyincorporated into the aqueous composition a crosslinking resin, forexample, an

amine aldehyde resin and/or an unsaturated methylol phenol ether.

The amine-aldehyde products employed herein are aldehyde condensationproducts of melamine, urea, benzoguanamine, or a similar compound. Theymay be water-soluble or they may be organic solvent-soluble. Generally,the aldehyde employed is formaldehyde, although useful products can bemade from other aldehydes, such as acetaldehyde, crotonaldehyde,acrolein, benzaldehyde, furfural, and others. Condensation products ofmelamine, urea and benzoguanamine are the most common and are preferred,but products of other amines and amides in which at least one aminogroup is present can also be employed.

For example, such condensation products can be produced from triazines,diazines, triazoles, guana dines, guanamines, and alkyl andaryl-substituted and cyclic ureas, and alkyl and aryl-substitutedmelamines. Some examples of such compounds are N,N'-dimethyl urea,benzyl urea, N,N'-ethylene urea, diazine diamine, formaguanamine,acetoguanamine, 2-chloro-4,6-diamine-1,3 ,S-triazine, 3,S-diaminotriazole, 4,6- diaminopyrimidine, 2,4,6-triphenyltriamine-1,3,5- triazine, and the like.

The aldehyde condensation products contain methylol groups or similaralkylol groups, depending upon the particular aldehyde employed.Ordinarily, in producing amine-aldehyde condensation products, all orpart of these methylol groups are etherified by reaction with an alcoholto produce an alkylated product. In the present invention, there areemployed those condensation products which are substantially completelyalkylated. By this it is meant that all or substantially all of themethylol groups have been etherified. Generally speaking, those productscontaining not more than an average of about one unalkylated alkylolgroup per molecule are utilized.

Various alcohols can be employed for the etherification of the alkylolgroups. These include essentially any monomeric alcohol, with thepreferred alcohols being methanol, ethanol, propanol, butanol, and otherlower alkanols having up to about 5 carbon atoms, including isomers suchas Z-methyl-l-propanol. There can also be employed alcohols such as thelower alkyl monoethers of ethylene glycol and the like; for instance,ethyl Cellosolve and butyl Cellosolve. Higher alcohols can be used butare less desirable because they tend to affect the film properties ofthe baked film. When the alkylated amine-aldehyde condensate is to beutilized in a vehicle to be employed in a waterdispersed coatingcomposition, it is preferred to employ a water-soluble alcohol in theetherification.

The amine-aldehyde condensation products are produced in a mannerwell-known in the art, using acidic or basic catalysts and varyingconditions of time and temperature. The aldehyde is often employed as asolution in water or alcohol, and the condensation, polymerization andetherification reactions may be carried out either sequentially orsimultaneously.

The methylolphenol ethers employed herein are compositions consistingessentially of one or more methylolphenol ethers of the formula:

l CH OH) where n is an integer from 1 to 3 and R is an unsatu ratedaliphatic group or a halogen-substituted unsaturated aliphatic group.The groups represented by R should contain at least 3 carbon atoms andcan be, for example, allyl groups (which are preferred) or others suchas methallyl, crotyl, butenyl, or the like. The halogen-substitutedunsaturated groups represented by R can be various monoandpoly-halogenated derivatives of the above unsaturated aliphatic groups,for example, 2-choroa1lyl, 3-chloroallyl, 3-chloro-2-methallyl,lchloro-Z-butenyl, and corresponding groups containing other halogenssuch as bromine and fluorine.

The methylolphenol ether compositions employed herein are described inUS. Pat. No. 2,579,330, and, as disclosed therein, can be produced fromsodium and barium salts or 2,4,6-tris(hydroxymethyl)phenols which areobtained by reacting formaldehyde with phenol in the presence of sodiumor barium hydroxide. Several methylolphenol ether compositions of thistype are commercially available and these generally comprise mixtures ofallyl ethers of mono-, diand trimethylol phenols (substituted in theortho, para and meta positions). The trimethylolated derivative isgenerally thepredominant component of the composition. Such commerciallyavailable methylol phenol ether compositions are preferred for use inthe invention.

The proportion of amine-aldehyde products and/or phenol ether andquaternary-containing resin in the coating composition can be variedconsiderably. The optimum amount employed depends upon the particularproperties desired in the product and also depends in part on theparticular quaternary onium groupcontaining resin. In the preferredproducts, the aminealdehyde products or the phenol ethers comprise fromabout 2 to about 30 percent by weight, based on the weight of thecombination with quaternary onium group-containing resins, although aslittle as 1 percent give some degree of improvement in properties of thecomposition and as much as about 50 percent can be utilized in somecases. Where both amine-aldehyde product and phenol ether are utilized,generally a combined weight of between about 1 percent and about 50percent by weightmay be employed, preferably between about 2 percent andabout 30 percent. The ratio of amine-aldehyde product and phenol etheris generally about lOO:l to 1:100, and preferably between about 5:1 and1:5.

Yet another crosslinking agent to the polymers of the inventioncontaining coreactive groups are capped or blocked isocyanatcs. Thecapped or blocked isocyanates which may be employed in the compositionsof the invention may be any isocyanate where the isocyanate groups havebeen reacted with a compound so that the resultant capped isocyanate isstable to amine groups at room temperature but reactive with aminegroups at elevated temperatures, usually between about 200 and about600F.

1n the preparation of the blocked organic polyisocyanate, any suitableorganic polyisocyanate may be used. Representative examples are thealiphatic compounds such as trimethylene, tetramethylene,pentamethylene, hexamethylene, 1,2-propylene, 1,2-butylene, 2,3-butylene, 1,3-butylene, ethylidine and butylidene diisocyanates; thecycloalkylene compounds such as 1,3- cyclopentane, 1,4-cyclohexane, and1,2-cyclohexane diisocyanates; the aromatic compounds such asmphenylene, p-phenylene, 4,4'-diphenyl, 1,5- naphthalene and1,4-naphthalene diisocyanates; the aliphatic-aromatic compounds such as4,4-

diphenylene methane, 2,4- or 2,6-tolylene, or mixtures thereof.4,4'-toluidin e and 1,4-xylylene diisocyanates; the nuclear substitutedaromatic compounds'such as dianisidine diisocyanate, 4,4'-diphenyletherdiisocyanate and chloro-diphenylene diisocyanate; the triisocyariatessuch as triphenyl methane-4,4,4- triisocyanate, 1,3,5-triisocyanatebenzene and 2,4,6- triisocyanate toluene; and the tetraisocyanates suchas 4,4"-diphenyl-dimethyl methane-2,2-5,5'- tetrai socyanate; thepolymerized polyisocyanates' such as tolylene diisocyanate dimers andtrimers, and the like. i

In addition, the organic polyisocyanate may be a prepolymer derived froma polyol including polyether polyol or polyester polyol, includingpolyethers which are reacted with excess polyisocyanates to formisocyanate terminated prepolymers may be simple polyols such as glycols,e.g., ethylene glycol and propylene glycol, as well as other polyolssuch as glycols, e.g., ethylene glycol and propylene glycol, as well asother polyols such as glycerol, trimethylolpropane, hexanetriol,pentaerythritol, and the like, as well as mono-ethers such as diethyleneglycol, tripropylene glycol and the like and polyethers, i.e., alkyleneoxide condensates of the above. Among the alkylene oxides that may becondensed with these polyols to form polyethers are ethylene oxide,propylene oxide, butylene oxide, styrene oxide and the like. These aregenerally called hydroxyterminated polyethers and can be linear orbranched. Examples of polyethers include polyoxyethylene glyccol havinga molecular weight of 1540, polyoxypropylene glycol having a molecularweight of 1025, polyoxytetramethylene glycol, polyoxyhexarnethyleneglycol, polyoxynonamethylene glycol, polyoxydecamethylene glycol,polyoxydodecamethylene glycol and mixtures thereof. Other types ofpolyoxyalkylene glycol ethers can be used. Especially useful polyetherpolyols are those derived from reacting polyols such as ethylene glycol,diethylene glycol, triethylene glycol, 1,4- butylene glycol,1,3-butylene glycol, 1,6-hexanediol, and their mixtures; glycerol,trimethylolethane, trimethylolpropane, l,2,6-hexanetriol,pentaerythritol, dipentaerythritol, tripentaerythritol,polypentaerythritol, sorbitol, methyl glucosides, sucrose and the likewith alkylene oxides such as ethylene oxide, propylene oxide, theirmixtures, and the like.

Any suitable aliphatic, cycloaliphatic or aromatic alkyl monoalcohol maybe used as a blocking agent in accordance with the present invention,such as, for example, aliphatic alcohols, such as methyl, ethyl, chloro-'ethyl','propyl, butyl, amyl, hexyl, heptyl, octyl, nonyl,

3,3,5-trimethylhexanol, decyl, and lauryl alcohols, and the like; thecycloaliphatic alcohols such as, for example, cyclopentanol,cyclohexanol, and the like, the aromatic-alkyl alcohols, such asphenylcarbinol, methylphenylcarbinol, and the like. Minor amounts ofeven higher molecular weight, relatively non-volatile monoalcohols maybe used, if desired, to serve as plasticizers in the coatings providedby this invention, Additional blocking agents include hydroxyl amines,such as ethanolamineand oximes such as methylethyl ketone oxime, acetoneoxime, and cyclohexanone oxime.

The organic polyisocyanate-blocking agent adduct is formed by reacting asufficient quantity of alcohol with the organic polyisocyanate to insurethat no free isocyanate groups are present. The reaction between the or-16 game polyisocyanate and the blocking agent is exothermic; therefore,the polyisocyanate and the blocking agent are preferably admixed attemperatures no higher than C.'and preferably, below 50C. to minimizethe exotherm effect.

Generally the amount of capped isocyanate employed with the resins ofthe invention is such as to provide between about 0.5 and about 2.0urethane groups per co-reactive group contained in the resin molecule.

The acid or acidic'solubilizing agent used with the compositions hereinis preferably any acid having a dissociation constant-greater than 1 X.10 Preferably, the acid or acidic solubilizing agent should be anorganic acid having adissociation constant greater than about 1 X 10'the presently preferred acid being lactic acid. The addition of acidaids in stabilizing the resin, since the epoxy may tend to furtherpolymerize on storage under highly alkaline conditions. In some casesthe acid also helps to obtain more complete dissolution of the resin. itis also-desirable to electrodeposit these coatings from an acidic oronly slightly basic solution (e.g., having a pH between about 3 andabout 8.5), and the addition of acid thus is ofteri'useful to achievethe desired pH.

The resin of the invention, when placed in a watercontaining medium,such as an electrodeposition high solids feed concentrate or theelectrodeposition bath, changes character. Since frequently theboron,'if present and chemically-bonded, is apparently weaklychemically-bound in the resin, it is subject to cleavage from theresin'molecule and, while the boron electrodeposits with the resin andis found in the electrodeposited film, the boron may be removed from thewater-containing medium in whole or in part by separation means, such aselectrodialysis or ultrafiltr ation, in the form of boric acid. l i IThe presence of a boron compound in the electrodeposited film is ofsubstantial benefit in that boron compounds apparently catalyze the cureof the deposited film, allowing lower cure temperatures and/or harderfilms. Where the resin is first prepared without the presence of boronand/or additional boron is desired when the resin is despersed, acompound of boron may be added, preferably boric acid or a precursorthereof.

The resin in aqueous medium can be characterized as a water-containingmedium containing an ungelled water-dispersible resin containingchemically-bound quaternary phosphonium base salts and optionallycontaining epoxy group 8. v

The resin preferably contains from about 0.1 to about 35 percent byweight phosphorous in the form of chemically-bound quaternaryphosphonium base salt groups; with the aqueous dispersion thereofcontaining in the preferred embodiment from about 0.01 to about 8percent by weight of boron contained in boric acid and/or a borate orboric acid complex.

The concentration of the product in water depends upon the processparameters to be used and is, in general, not critical, but ordinarilythe major proportion of the aqueous composition is water, e .g., thecomposition may contain from one to 25 percent by weight of the resin.

Preferably, the electrodepositable compositions of the invention containa coupling solvent. The use of a coupling solvent provides for improveddeposited film appearance. These solvents include hydrocarbons, al-

coholsyesters, ethers.'and ketones. The preferred coupling solventsinclude monoalcohols; glycols, and polyols'as well as ketones'a-nd etheralcohols. Specific coupling solvents include. isopropanol,butanol,.isophorone,-Pentoxone (4-methoxy-4-methyl pentanone-Z),ethylene and propylene glycol, the monomethyl, monoethyl and monobutylethers ofethylene glycol, 2- ethylhexanol and hexyl Cellosolve. Thepresently preferred coupling solvent is 2-ethyhexanol. The amount ofsolvent is not unduly critical, generally between about 0.1 and about 40percent by weight of the dispersant may be employed, preferably betweenabout 0.5 and about 25 percent by weight of the dispersant is employed.

While the resins hereinabove described may be electrodeposited assubstantially the sole resinous component of the electrodepositedcomposition, as noted earlier it is frequently desirable in order toimprove or modify film appearance and/or film properties, to incorporateinto the .electrodepositable compositions various non-reactive andreactive compounds or resinous materials such as .plasticizing material,including N-cyclohexyl-p-toluene sulfonamide, orthoand paratoluenesulfonamide, N-ethyl-orthoand para-toluene sulfonamide, aromatic andaliphatic polyether polyols, phenol resins including allyl ethercontaining phenolic resins, liquid epoxy resins, quadrols,polycaprolactones; triazine resins such as melamine-based resins andbenzoguanamine-based resins, especially alkylated formaldehyde reactionproducts thereof; urea formaldehyde resins, acrylic resins, hydroxyand/or carboxyl group-containing polyesters and hydrocarbon resins.

Other materials include esters such as butylbenzyl phthalate, dioctylphthalate, methyl phthalylethyl glycolate, butylphthalylbutyl glycolate,cresyl diphenyl phosphate, 2-ethylhexyl diphenyl phosphate, polyethyleneglycol 200 dibenzoates, as well as polyesters, 2,2,4- trimethylpentanediol 'monoisobutyrate (Texanol).

In most instances, a pigment composition and, if desired, variousadditives such as anti-oxidants, surfactants, or wetting agents, forexample, Foam Kill 639 (a hydrocarbon oil-containing inert diatomaceousearth), as well as glycolated acetylenes (the Surfynols, for example),sulfonates, sulfated fatty amides, and alkylphenoxypolyoxyalkylenealkanols, and the like, are included. The pigment composition may be ofany conventional type, comprising, for example, iron oxides, leadoxides, strontium chromate, carbon black, titanium dioxide, talc, bariumsulfate, as well as color pigments such as cadmium yellow, cadmium red,chromic yellow, and the like.

In the electrodeposition processes employing the aqueous coatingcompositions described above, the aqueous composition is placed incontact with an electrically-conductive anode and anelectricallyconductive cathode, with the surface to be coated being thecathode, while in contact with the bath containing the coatingcomposition, an adherent film of the coating composition is deposited onthe cathode. This is directly contrary to the processes utilizingpolycarboxylic acid resins. as in the prior art, and the advantagesdescribed are, in large part, attributed to this cathodic deposition.

The conditions under-which the electrodeposition is carriedout are, ingeneral, similar to those used in electrodeposition of other'type's ofcoatings. The applied .which forms the salt migrates at least in parttoward the anode. Where the electrodeposition bath contains boron, theelectrodeposited resin further contains boron which may be bonded withthe basic groups present in the film which has electrodeposited upon thecathode. The amounts of bonded boron in the electrodeposited filmapparently increases with increasing boron concentration in the bath toa saturation value, dependent on the number of basic groups in theconcentration and the basicity of the base groups. It is also possiblethat upon deposition the quaternary phosphonium salt dissociates to anessentially uncharged state.

The film, while it may be crosslinked to'some extent, remains soluble incertain organic solvents.

The method of the invention is applicable to the coating of anyconductive substrate, and especially metals such as steel,.aluminum,copper, magnesium or the like. After deposition, the coating is cured,usually be baking at elevated temperatures. Temperatures of 250to 500F.for l to 30 minutes are typical baking schedules utilized.

During the cure, especially at elevated temperatures, it is believedthat at least a substantial portion of the quaternary phosphonium basedecomposes to phosphines (assuming, as noted above, that quaternaryphosphonium groups are present in the deposited film), which aids in thecrosslinking of the coatings, which upon curing is infusible andinsoluble. The presence of boron salts and complexes in the filmincreases the rate of crosslinking reduces the temperatures necessaryfor acceptable curing in commercially-reasonable times and producescoatings with improved hardness and corrosion resistance. I

As set forth above, the significant resin constituents are (A) a resinderived from an epoxy-containing organic material, and optionallycontaining oxyalkylene groups (B) quaternary phosphonium groups, assalts of acids preferably having a dissociation constant greater than l-X 10 and, optionally, (C) boron and (D) epoxy groups. All thesecomponents may be qualitatively determined by numerous methods known inthe art. I

Epoxy groups may be determined by the well-known pyridinium hydrocloridemethod as described, for exvoltage may be varied greatly and can be forexample, a

ample, in Siggia, QUANTITATIVE ORGANIC ANALYSIS VIA FUNCTIONAL GROUPS,John Wiley & Sons, Inc., New York (1963), page 242.

The total base groups present in the polymer, including quaternarygroups present, may be determined on a separate resin sample. Usuallythe'resin sample will be neutral. If, however, the resinisbasic, thesample should be neutralized witha known amount of the acid present inthe resin as a salt. Where the acid present in the resin as a salt aweak acid as compared to HCl, the resin is titrated as HC( andback-titrated with sodium hydroxide on an automatic titratorf' The HCltitration yields the total base groups present. For example,

.,a typical analysis is conducted as follows: a 10 milliliter sample ofan about percent solids electrodeposition bath is pipetted into 60milliliters of tetrahydrofuran. The sample is titrated with 0.1000normal HCl to the pH end point. The amount of standard acid used isequivalent to the quaternary base present. The sample is then backtitrated with 0.1000 normal sodium hydroxide to give a titration curvewith multiple end points. In a typical instance, the first end pointcorresponds to excess HCI. From the HCL titration, the second end pointcorresponds to the neutralization of the weak acid (for example, lacticacid). The difference in volume between the two endpoints gives thevolume of standard base equivalent to the weak acid content of thesample.

Whereas solvent such as propylene glycol is employed with, for exampletetrahydrofuran to maintain sample homogeneity, boron present will alsotitrate since the boron in the form present forms an acid complex withthe propylene glycol. Under the conditions specified, the boric acid maybe distinguished from the weak acid (e.g., lactic) by an additionalinflection point in the pH titration curve.

In the case of the presence of acid salts of strong acids, other methodsmust be employed to determine acid, and quaternary groups present. Forexample, where the resin contains quaternary hydrochloride groups, theresin may be dispersed, for example, in a mixture of glacial acetic acidand tetrahydrofuran, the chloride complexed with mercuric acetate andthe sample titrated with perchloric acid to yield the quaternary groups.

Boron may be determined as described by R. S. Braman, BoronDetermination, ENCYCLOPEDIA OF INDUSTRIAL CHEMICAL ANAYSIS, F. D. Snelland Hilton, Editors, John Wiley & Sons, Inc., New York (1968), Volume 7,pages 384423. The boron may be determined on a separate sample. Forexample, by pipetting a 10 milliliter sample of an approximately 10percent solid cationic electrodeposition bath into 60 milliliters ofdistilled water. Sufficient HCl is then added to lower the pH to about4.0. The sample is then back-titrated with 0.1000 normal sodiumhydroxide, using a Metrohm Potentiograph E-436 automatic titrator orequivalent apparatus, to the first inflection point in the pH titrationcurve. There is then added 7 grams of mannitol. The solution becomesacid and titration is then continued to the second inflection point inthe pH titration curve. The amount of base consumed between the firstand second end points is the measure of the number of moles of boricacid complex formed in the sample.

The above description is exemplary of the technique employed toquantitatively and qualitatively identify the groups present. Inspecific case, analytical techniques may be adapted to a specific resin;however, in each case, consistent with the above description, thereexist methods known in the art which yield appropriate accuratedeterminations of the significant chemical moiety content.

Illustrating the invention are the following examples, which, however,are not to be construed as limiting the invention to their details. Allparts and percentages in the examples, as well as throughout thisspecification, are by weight unless otherwise specified.

EXAMPLE I Into a reactor equipped with a thermometer. stirrer, additionmeans and inert gas blanket were charged I00 parts of Epon 836 and 16parts of butyl Cellosolve. This mixture was heated to 45C. with stirringand then there were added 30 parts of tributyl phosphine and 16 parts of85 percent lactic acid. The reaction was exothermic and the temperaturerose to C. There was then added 10 parts of water and this mixture heldan additional 20 minutes at a reaction temperature of 78C. After anadditional 25 minutes at 80C.. there was added 34 parts of water and thetemperature dropped to 72C. After an additional 30 minutes, thetemperature had risen to C. and a clear resin solu? tion was obtained.The reaction product had the following values, adjusted to percentsolids:

Epoxy value Hydroxyl value EXAMPLE ll Into a reactor equipped withthermometer, stirrer, addition means and an inert gas blanket werecharged 354 parts of Epon 829 and 60 parts of bisphenol A. The reactionmixture was heated to 175C. and an exotherm was noted to 186C. Thereaction mixture was held for 45 minutes at 186C. The reactiontemperature was then dropped to C. and there was then added parts ofpolypropylene glycol with a molecular weight of approximately 600,together with 1.1 part of dimethyl ethanolamine. The reaction mixturewas held at 140C. for 5.5 hours until the reaction mixture had aGardner-Holdt viscosity of L-K, measured in a 50 percent solution of90/10 isophorone/toluene. This 50 percent solution had a hydroxyl valueof I31 and an epoxy value of 1643. There was added a small amount offormic acid to neutralize the amine catalyst.

At a reaction temperature of 53C. there was added 85 parts oftetrahydrofuran and a slurry of 36.4 parts of tributyl phosphine and19.1 parts of 85 percent lactic acid. After 5 minutes, 20 parts of waterwere added and an additional 18.2 parts of tributyl phosphine and 9.55parts of 85 percent lactic acid. After an additional 5 hours, there wasadded an additional 18.2 parts of tributyl phosphine and 9.55 parts of85 percent lactic acid. The reaction mixture was held for an additional5 hours, at which point the 81.2 percent solids reaction product had ahydroxyl value of I69 and an epoxy value of 4390.

An electrodeposition bath was prepared by admixing 615. parts of theabove reaction mixture together with 15 parts of butyl Cellosolve and423.5 parts of water. The electrodeposition bath was approximately 10percent solids.

Aluminum and steel panels were electrocoated at between 100 and ISOvolts for one minute at room temperature. The panels after baking for 30minutes at 350F. yielded a yellow film with a 3H pencil hardness with afilm thickness of 0.5-0.6 mil. The film displayed appreciablethermosetting character having fair acctone resistance.

EXAMPLE 111 lnto a reactor equipped with thermometer. stirrer.condenser, inert gas blanket and heating means were charged 354 parts ofEpon 829 and 60 parts of bispheno] A. The reaction mixture was heated to170C., at which time an exotherm was noted. The temperature wasmaintained at 175C. for 1 hour and was then allowed to cool. When thetemperature had reached l40C., 170 parts of polypropylene glycol with amolecular weight of about 600 was added to the reaction mixture. After 5minutes (temperature 135C.), 1.1 part of dimethylethanolamine was addedto the reaction mixture. The reaction mixture was held at 135C. for 5hours and 25 minutes and was then allowed to cool. There was then addeda small amount of formic acid (1.8 parts in a 90 percent aqueoussolution) to neutralize the amine catalyst. Cooling of the reactionmixture was continued and when the temperature had reached 65C., 152.7parts of tetrahydrofuran were added to the mixture. The mixture wascooled to 53C., at which time 69 parts of tributyl phosphine and 36.2parts of lactic acid (85 percent aqueous solution) were added thereto.After 5 minutes, 36 parts of water were added, and the temperature wasthereafter held at 52C. for about 5 hours. There was then added to thereaction mixture and additional 34.5 parts of tributyl phosphine and18.1 parts of the lactic acid. The temperature was maintained at 50C.for another 55 minutes, at which time an additional 34.5 parts oftributyl phoshine and 18.1 parts oflactic acid were added. The reactionmixture was held for an additional 4 hours and minutes at about 50C. andwas then allowed to cool. The resultant product was analyzed to consistof 77.7 percent solids with an infinite epoxy equivalent and an hydroxylvalue of 99.

An electrodeposition bath was prepared by admixing 246 parts of theabove reaction product and 60 grams of butyl Cellosolve. Water was thenadded to the resinsolvcnt blend while agitating the mixture, reducingthe solids content to 10 percent. Aluminum panels were electrodepositedat 100 volts for 60 seconds at room temperature and were then baked at385F. for minutes. The baked film, having a pencil hardness of 2H,exhibited poor acetone resistance, being completely removed from thepanel after 10 rubs.

To the above bath were added 23.3 parts of boric acid (4.5 percentaqueous solution). Aluminum panels were then electrodeposited and bakedunder the same conditions as the boron-free bath. The baked film, havinga pencil hardness of 2H, exhibited improved acctone resistance, beingsoftened but not removed after 10 rubs.

The throwpower of both compositions was one inch when deposited at 100volts for 60 seconds at 80F.

Other reaction products can be formed and utilized in the foregoinginvention using other epoxy compounds, phosphines, acids, salts andboron compounds as described above. Similarly, other conditions andadjuvants and the like may be employed to formulate and utilize thecoating compositions as desired.

According to the provisions of the Patent Statutes, there are describedabove the invention and what are now considered to be its bestembodiments; however, within the scope of the appended claims, it is tobe understood that the invention can be practiced otherwise than asspecifically described.

We claim:

1. In a method of coating a conductive substrate serving as a cathode,which method comprises passing electric current between an anode andsaid cathode in electrical contact with a water-dispersed composition,the improvement wherein the water-dispersed composition is awater-dispersible, quaternary phosphonium saltcontaining resincomprising the reaction product of:

A. an epoxy group-containing organic material. and

B. a phosphine-acid mixture, said phosphine-acid mixture reacted withsaid organic material in an amount and at a temperature sufficient toprovide a quaternary phosphonium salt-containing, water-dispersibleresin.

2. The method of claim 1 wherein said reaction product contains epoxygroups.

3. The method of claim 1, wherein said reaction product is essentiallyepoxy group free.

4. The method of claim 1 wherein said reaction product contains in theresin molecule at least about 0.1 percent by weight of chemically-boundphosphorous in the form of a quaternary phosphonium base salt.

5. The method of claim 4 wherein said quaternary phosphonium base saltis the salt of an acid having a dissociation constant greater than about1 X 10*.

6. The method of claim 1 wherein said organic material is a polyglycidylether of a polyphenol.

7. The method of claim 1 wherein the aqueous dispersion further containsboric acid.

8. The method of claim 1 wherein said quaternary phosphoniumsalt-containing resin contains oxyalkylene groups.

9. The method of claim 1 wherein said salt is the salt of an organicacid.

10. The method of claim 1 wherein said reaction product containschemically-bound boron in the resin molecule.

11. The method of claim 1, wherein said reaction product contains in theresin molecule from about 0.1 to about 35 percent by weight ofchemically-bound phosphorous in the form of a quaternary phosphonium

1. IN A METHOD OF COATING A CONDUCTIVE SUBSTRATE SERVING AS A CATHODE,WHICH METHOD COMPRISES PASSING ELECTRIC CURRENT BETWEEN AN ANODE ANDSAID CATHODE IN ELECTRICAL CONTACT WITH A WATER-DISPERSED COMPOSITION,THE IMPROVEMENT WHEREIN THE WATER-DISPERSED COMPOSITION IS AWATER-DISPERSIBLE, QUATERNARY PHOSPHONIUM SALT-CONTAINING RESINCOMPRISING THE REACTION PRODUCT OF: A. AN EPOXY GROUP-CONTAINING ORGANICMATERIAL, AND B. A PHOSPHINE-ACID MIXTURE, SAID PHOSPHINE-ACID MIXTUREREACTED WITH SAID ORGANIC MATERIAL IN AN AMOUNT AND AT A TEMPERATURESUFFICIENT TO PROVIDE A QUATERNARY PHOSPHONIUM SALT-CONTAINING,WATER-DISPERSIBLE RESIN.
 2. The method of claim 1 wherein said reactionproduct contains epoxy groups.
 3. The method of claim 1, wherein saidreaction product is essentially epoxy group free.
 4. The method of claim1 wherein said reaction product contains in the resin molecule at leastabout 0.1 percent by weight of chemically-bound phosphorous in the formof a quaternary phosphonium base salt.
 5. The method of claim 4 whereinsaid quaternary phosphonium base salt is the salt of an acid having adissociation constant greater than about 1 X 10
 5. 6. The method ofclaim 1 wherein said organic material is a polyglycidyl ether of apolyphenol.
 7. The method of claim 1 wherein the aqueous dispersionfurther contains boric acid.
 8. The method of claim 1 wherein saidquaternary phosphonium salt-containing resin contains oxyalkylenegroups.
 9. The method of claim 1 wherein said salt is the salt of anorganic acid.
 10. The method of claim 1 wherein said reaction productcOntains chemically-bound boron in the resin molecule.
 11. The method ofclaim 1, wherein said reaction product contains in the resin moleculefrom about 0.1 to about 35 percent by weight of chemically-boundphosphorous in the form of a quaternary phosphonium base salt.